Critics say lawmakers took a step to dismantle the statewide campaign finance reform initiative passed last November by Colorado voters.
House Bill 1132 passed on a narrow 33-31 vote. It faces a third reading before going to the Senate.
Opponents say it will allow political officeholders to set up "office accounts'' to get around the spending caps and pepper voters with unlimited campaign messages.
They also say it will allow anonymous attack pamphlets to continue by broadly defining newspapers exempt under the current law amendment.
Republican Representative Rob Fairbank of Littleton says the bill is intended to implement the amendment passed by voters, not circumvent it.